1. Field of the Invention
Embodiments of the invention relate generally to voltage reference generation, and specifically to internal voltage reference generation for a DDR memory interface.
2. Background Information
Packaging costs are a significant part of the cost of semiconductor devices. Typically the greater number of pins or terminals in a package the greater is the costs of the package. Moreover, pins or terminals of a package require space in order to make a connection such as to a printed circuit board. If the requirements for a pin or terminal can be eliminated in an interface, the package costs may be reduced or otherwise the unused pin can be assigned to a different function, such as an extra pin or terminal for power or ground.
Voltage references with known voltage levels may be used for comparison with unknown levels of input signals to make some determination about the unknown levels. The voltage references used for such comparisons may be generated in a number of ways. A voltage reference may be generated externally and coupled into an integrated circuit (IC) through a dedicated voltage reference pin or terminal of a package for use by circuits therein. In this case, the semiconductor die of the IC has a dedicated voltage reference pad to couple to the voltage reference pin or terminal of the package.
The use of a dedicated voltage reference pin or terminal of a package increases the package costs. Additionally, the use of the dedicated voltage reference pin or terminal also increases the costs of the semiconductor die of the IC by accommodating the dedicated pad for the external voltage reference.